Laminated inductors generally have a structure in which a plurality of insulating layers, including conductive patterns, are stacked. Such conductive patterns are commonly sequentially connected by conductive vias formed in the insulating layers and overlapped in a stacking direction, thereby forming a coil having a spiral structure. In addition, both ends of the coil may extend outwards from surfaces of the laminated structure, to be connected to an external terminal.
Inductors are mainly surface mounted devices (SMD) mounted on a circuit board. In particular, high-frequency inductors, used for signals within a high frequency band, equal to or higher than 100 MHz, have recently been increasingly used in the telecommunications market. One important issue related to the use of high-frequency inductors is to ensure sufficient quality-factor (Q-factor) characteristics, representing the efficiency of a chip inductor, therein. Here, the symbol Q, as expressed mathematically, Q=wL/R, is a ratio of inductance L to resistance R in a given frequency band.
Since an inductor is manufactured in accordance with a specific nominal inductance value L, resistance R needs to be lowered in order to enhance Q-characteristics at the same inductance value L. In order to lower resistance R, a thickness of a coil pattern may be increased. A coil pattern may be formed using a screen printing method, a method in which limitations exist in increasing the thickness of the coil pattern. In addition, when a relatively thick coil pattern is formed on a ceramic layer, failures such as cracking and delamination may occur during a process of stacking a plurality of sheets including the coil patterns, due to a difference in thickness between a portion of a sheet on which a coil pattern is formed and a portion of a sheet on which a coil pattern is not formed.
Furthermore, vias connecting the coil patterns may be formed by electroplating a metal or by printing a conductive paste (a metal paste). When the vias are formed by the electroplating method, interlayer insulating distances may not be uniform, since hardness of the metal increases during the process of stacking the plurality of sheets. When the vias are formed using the conductive paste, however, Q-characteristics may be degraded, since the resistance of the coil may be increased.
Accordingly, research has been conducted into a structure of an inductor ensuring a uniform insulating distance while also reducing the resistance of the coil.